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  • Circle to Circle collision, checking each circle against all others

    - by user14861
    I'm currently coding a little circle to circle collision demo but I've got a little stuck. I think I currently have the code to detect collision but I'm not sure how to loop through my list of circles and check them off against one another. Collision check code: public static Vector2 GetIntersectionDepth(Circle a, Circle b) { float xValue = a.Center.X - b.Center.X; float yValue = a.Center.Y - b.Center.Y; Vector2 depth = Vector2.Zero; float distance = Vector2.Distance(a.Center, b.Center); if (a.Radius + b.Radius > distance) { float result = (a.Radius + b.Radius) - distance; depth.X = (float)Math.Cos(result); depth.Y = (float)Math.Sin(result); } return depth; } Loop through code: Vector2 depth = Vector2.Zero; for (int i = 0; i < bounds.Count; i++) for (int j = i+1; j < bounds.Count; j++) { depth = CircleToCircleIntersection.GetIntersectionDepth(bounds[i], bounds[j]); } Clearly I'm a complete newbie, wondering if anyone can give any suggestions or point out my errors, thanks in advance. :)

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  • LWJGL Java 2D collision when lagging

    - by user1990950
    I'm using a tile based collision, but when the game is lagging (the lag isn't the problem) the collision fails and the player falls through tiles. This is the movement/collision detection code of my Player class: gravity.y = gspeed; speed.y+=gravity.y; position.set(position.x + direction.x * speed.x * deltaSeconds, position.y + direction.y * speed.y * deltaSeconds); for (int i = (int) Math.round(position.x / 32) - 2 * t; i < (int) Math.round(position.x / 32) + 3 * t; i++) { for (int j = (int) Math.round(position.y / 32); j < (int) Math.round((position.y + height + 64) / 32); j++) { checkCollision(i, j, deltaSeconds); } } public void checkCollision(int i, int j, float deltaSeconds) { bbox.setBounds((int) position.x, (int) position.y, (int) width, (int) height); Tile t = null; t = Map.getTile(i, j); if (t != null) { if (t.isSolid()) { if (t.getTop().intersects(bbox)) { if (position.y + height < t.y * 32 + 32) { if (speed.y >= 0) { position.y = t.y * 32 - height; speed.y = 0; gravity.y = 0; jumpState = 0; } } } if (t.getBottom().intersects(bbox)) { if (position.y < t.y * 32 + 32) { position.y = t.y * 32 + 32; speed.y = 0; } } else { if (t.getLeft().intersects(bbox)) { if (position.x + width > t.x * 32) { position.x = t.x * 32 - width; speed.x = 0; } } if (t.getRight().intersects(bbox)) { if (position.x < t.x * 32 + 32) { position.x = t.x * 32 + 32; speed.x = 0; } } } } } } Is it possible to fix my code, if yes how? Or is it possible to tell if the game is lagging?

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  • Big level objects collision system for 2d game

    - by Aristarhys
    I read many variants today and get some knowledge in general, so here is a steps of mine thoughts in pictures (horrible paint.net ones). We need to develop grid system, so we check only thing near, perform simple check to cut out deep check, and at - last deep check like per-pixel collision check. Step 1 - Let p1, p2 are some sprites lets first just check with circle collision - because large distance between p1, p2 this fails and of course so we don't need test more deeply. But if we have not 2, but 20 objects, why we need to even circle test something so far outside of our view. Step 2 - Add basic column system, now we don't bother with p2 if it's in a column far from p1 column, so we even don't do circle test. But p3 is in the same col, so let do circle test, which of course will fail. Step 3 - Lets improve column system to the grid system with grid cell size just like p1, p2, p3 collision boxes, so we cut out things much top or below p1. And this is all great until comes BIG OBJs which is some kind of platforms. They are much bigger then grid cell. Circle test for will be successful, but deep check for whole big obj will fail And that the part I can't get. How do I store the grid position of big object? Like 4 grid coords for big object vertexes? And if one of them close to p1 do circle check for centre of big object then a deep one if succeed? Am I do it wrong? My possible solution:

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  • Colored Collision Detection

    - by tugrul büyükisik
    Several years ago, i made a fast collision detection for 2D, it was just checking a bullets front-pixel's color to check if it were to hit something. Lets say the target rgb color is (124,200,255) then it just checks for that color. After the collision detection, it paints the target with appropriate picture. So, collision detection is made in background without drawing but then painted and drawed. How can i do this in 3D? Because, a vertex is not just exist like a 2D picture's pixel. I looked at some java3D and other programs and understood that 3D world is made of objects. Not just pictures. Is there a program that truly fills the world with vertices ? But it could be needing terabytes of ram even more. Do you know an easy way to interpolate the color of a vertex in java3D or similar program? Note: for a rgb color-identifier, i can make 255*255*255 different 2D objects in background.

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  • Android Bitmap: Collision Detecting

    - by Aekasitt Guruvanich
    I am writing an Android game right now and I would need some help in the collision of the Pawns on screen. I figured I could run a for loop on the Player class with all Pawn objects on the screen checking whether or not Width*Height intersects with each other, but is there a more efficient way to do this? And if you do it this way, many of the transparent pixel inside the rectangular area will also be considered as collision as well. Is there a way to check for collision between Bitmap on a Canvas that disregard transparent pixels? The class for player is below and the Pawn class uses the same method of display. Class Player { private Resources res; // Used for referencing Bitmap from predefined location private Bounds bounds; // Class that holds the boundary of the screen private Bitmap image; private float x, y; private Matrix position; private int width, height; private float velocity_x, velocity_y; public Player (Resources resources, Bounds boundary) { res = resources; bounds = boundary; image = BitmapFactory.decodeResource(res, R.drawable.player); width = image.getWidth(); height = image.getHeight(); position = new Matrix(); x = bounds.xMax / 2; // Initially puts the Player in the middle of screen y = bounds.yMax / 2; position.preTranslate(x,y); } public void draw(Canvas canvas) { canvas.drawBitmap(image, position, null); } }

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  • Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

    - by Prog
    In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the entities (i.e. where the entities 'act': update their positions, invoke AI, etc) is in a different class, in the method updateEntities(List<Entity> entities). Also called from the gameloop, after the collision detection. When there's a collision between two entities, usually something needs to be done. For example, zero the velocity of both entities in the collision, or kill one of the entities. It would be easy to have this code in the CollisionDetector class. E.g. in psuedocode: for(Entity entityA in entities){ for(Entity entityB in entities){ if(collision(entityA, entityB)){ if(entityA instanceof Robot && entityB instanceof Robot){ entityA.setVelocity(0,0); entityB.setVelocity(0,0); } if(entityA instanceof Missile || entityB instanceof Missile){ entityA.die(); entityB.die(); } } } } However, I'm not sure if updating the state of entities in response to collision should be the job of CollisionDetector. Maybe it should be the job of EntityUpdater, which runs after the collision detection in the gameloop. Is it okay to have the code responding to collisions in the collision detection system? Or should the collision detection class only detect collisions, report them to some other class and have that class affect the state of the entities?

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  • simple collision detection with box2dweb

    - by skywalker
    im beginner in box2dweb that version of box2d for javascript i wrote simple gravity system and i want to detect the collision between the box and the ground , when the falling box hit the ground execute simple function like function sucs(){alert("the box on the floor !")}; this is my code var CANVAS_WIDTH = 1024, CANVAS_HEIGHT = 700, SCALE = 30; var b2Vec2 = Box2D.Common.Math.b2Vec2 , b2BodyDef = Box2D.Dynamics.b2BodyDef , b2Body = Box2D.Dynamics.b2Body , b2FixtureDef = Box2D.Dynamics.b2FixtureDef , b2Fixture = Box2D.Dynamics.b2Fixture , b2World = Box2D.Dynamics.b2World , b2MassData = Box2D.Collision.Shapes.b2MassData , b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape , b2CircleShape = Box2D.Collision.Shapes.b2CircleShape , b2DebugDraw = Box2D.Dynamics.b2DebugDraw; var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d"); var world = new b2World(new b2Vec2(0, 8), true); var fixDef = new b2FixtureDef(); var bodyDef = new b2BodyDef(); fixDef.density = 1.0; fixDef.friction = 0.5; bodyDef.type = b2Body.b2_staticBody; fixDef.shape = new b2PolygonShape; fixDef.shape.SetAsBox(20, 2); bodyDef.position.Set(10, 400 / 30 + 1.8); world.CreateBody(bodyDef).CreateFixture(fixDef); fixDef.density = 1.0; fixDef.friction = 0.5; fixDef.restitution = 0.3; bodyDef.type = b2Body.b2_dynamicBody; bodyDef.position.Set(50 / SCALE, 0 / SCALE); //bodyDef.linearVelocity.Set((Math.random() * 12) + 2, (Math.random() * 12) + 2); fixDef.shape = new b2PolygonShape(); fixDef.shape.SetAsBox(25 / SCALE, 25 / SCALE); world.CreateBody(bodyDef).CreateFixture(fixDef); var debugDraw = new b2DebugDraw(); debugDraw.SetSprite(document.getElementById("canvas").getContext("2d")); debugDraw.SetDrawScale(30.0); debugDraw.SetFillAlpha(0.5); debugDraw.SetLineThickness(1.0); debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit); world.SetDebugDraw(debugDraw); var image = new Image(); image.src = "image.png"; window.setInterval(gameLoop, 1000 / 60); function gameLoop() { world.Step(1 / 60, 8, 3); world.ClearForces(); context.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT); b = world.GetBodyList() var pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); b = b.GetNext(); pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); //b.GetAngle()++; context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); world.DrawDebugData(); };

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  • 2D Tile based Game Collision problem

    - by iNbdy
    I've been trying to program a tile based game, and I'm stuck at the collision detection. Here is my code (not the best ^^): void checkTile(Character *c, int **map) { int x1,x2,y1,y2; /* Character position in the map */ c->upY = (c->y) / TILE_SIZE; // Top left corner c->downY = (c->y + c->h) / TILE_SIZE; // Bottom left corner c->leftX = (c->x) / TILE_SIZE; // Top right corner c->rightX = (c->x + c->w) / TILE_SIZE; // Bottom right corner x1 = (c->x + 10) / TILE_SIZE; // 10px from left side point x2 = (c->x + c->w - 10) / TILE_SIZE; // 10px from right side point y1 = (c->y + 10) / TILE_SIZE; // 10px from top side point y2 = (c->y + c->h - 10) / TILE_SIZE; // 10px from bottom side point /* Top */ if (map[c->upY][x1] > 2 || map[c->upY][x2] > 2) c->topCollision = 1; else c->topCollision = 0; /* Bottom */ if ((map[c->downY][x1] > 2 || map[c->downY][x2] > 2)) c->downCollision = 1; else c->downCollision = 0; /* Left */ if (map[y1][c->leftX] > 2 || map[y2][c->leftX] > 2) c->leftCollision = 1; else c->leftCollision = 0; /* Right */ if (map[y1][c->rightX] > 2 || map[y2][c->rightX] > 2) c->rightCollision = 1; else c->rightCollision = 0; } That calculates 8 collision points My moving function is like that: void movePlayer(Character *c, int **map) { if ((c->dirX == LEFT && !c->leftCollision) || (c->dirX == RIGHT && !c->rightCollision)) c->x += c->vx; if ((c->dirY == UP && !c->topCollision) || (c->dirY == DOWN && !c->downCollision)) c->y += c->vy; checkPosition(c, map); } and the checkPosition: void checkPosition(Character *c, int **map) { checkTile(c, map); if (c->downCollision) { if (c->state != JUMPING) { c->vy = 0; c->y = (c->downY * TILE_SIZE - c->h); } } if (c->leftCollision) { c->vx = 0; c->x = (c->leftX) * TILE_SIZE + TILE_SIZE; } if (c->rightCollision) { c->vx = 0; c->x = c->rightX * TILE_SIZE - c->w; } } This works, but sometimes, when the player is landing on ground, right and left collision points become equal to 1. So it's as if there were collision coming from left or right. Does anyone know why this is doing this?

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  • Resolving bounding box collision detection

    - by ndg
    I'm working on a simple collision detection and resolution method for a 2d tile-based bounding box system. Collision appears to work correctly, but I'm having issues with resolving a collision after it has happened. Essentially what I'm attempting to do is very similar to this approach. The problem I'm experiencing is that because objects can be traveling with both horizontal and vertical velocity, my resolution code causes the object to jump incorrectly. I've drawn the following annotation to explain my issue. In this example, because my object has both horizontal and vertical velocity, my object (which is heading upwards and collides with the bottom of a tile) has it's position altered twice: To correctly adjust it's vertical position to be beneath the tile. To incorrectly adjust it's horizontal position to be to the left of the tile. Below is my collision/resolution code in full: function intersects(x1, y1, w1, h1, x2, y2, w2, h2) { w2 += x2; w1 += x1; if (x2 > w1 || x1 > w2) return false; h2 += y2; h1 += y1; if (y2 > h1 || y1 > h2) return false; return true; } for(var y = 0; y < this.game.level.tiles.length; y++) { for(var x = 0; x < this.game.level.tiles[y].length; x++) { var tile = this.game.level.getTile(x, y); if(tile) { if( this.velocity.x > 0 && intersects(this.position.x+dx+this.size.w, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)-this.size.w); hitSomething = true; break; } else if( this.velocity.x < 0 && intersects(this.position.x+dx, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)+tileSize); hitSomething = true; break; } if( this.velocity.y > 0 && intersects(this.position.x+dx, this.position.y+dy+this.size.h, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)-this.size.h); hitSomething = true; break; } else if( this.velocity.y < 0 && intersects(this.position.x+dx, this.position.y+dy, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)+tileSize); hitSomething = true; break; } } } } if(hitSomething) { this.velocity.x = this.velocity.y = 0; dx = dy = 0; this.setJumping(false); }

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  • Collision 2D Quads

    - by Vico Pelaez
    I want to detect collision between two 2D squares, one square is static and the other one moves according to keyboard arrows. I have implemented some code, however nothing happens when they overlap each other and what I tried to achieve in the code was to detect an overlapping between them. I think I am either not understanding the concept really well or that because one of the squares is moving this is not working. Please I would really appreciate your help. Thank you! float x1=0.05 ,Y1=0.05; float x2=0.05 ,Y2=0.05; float posX1 =0.5, posY1 = 0.5; float movX2 = 0.0 , movY2 = 0.0; struct box{ int width=0.1; int heigth=0.1; }; void init(){ glClearColor(0.0, 0.0, 0.0, 0.0); glColor3f(1.0, 1.0, 1.0); } void quad1(){ glTranslatef(posX1, posY1, 0.0); glBegin(GL_POLYGON); glColor3f(0.5, 1.0, 0.5); glVertex2f(-x1, -Y1); glVertex2f(-x1, Y1); glVertex2f(x1,Y1); glVertex2f(x1,-Y1); glEnd(); } void quad2(){ glMatrixMode(GL_PROJECTION); glLoadIdentity(); glPushMatrix(); glTranslatef(movX2, movY2, 0.0); glBegin(GL_POLYGON); glColor3f(1.5, 1.0, 0.5); glVertex2f(-x2, -Y2); glVertex2f(-x2, Y2); glVertex2f(x2,Y2); glVertex2f(x2,-Y2); glEnd(); glPopMatrix(); } void reset(){ //Reset position of square??? movX2 = 0.0; movY2 = 0.0; collisionB = false; } bool collision(box A, box B){ int leftA, leftB; int rightA, rightB; int topA, topB; int bottomA, bottomB; //Calculate the sides of box A leftA = x1; rightA = x1 + A.width; topA = Y1; bottomA = Y1 + A.heigth; //Calculate the sides of box B leftB = x2; rightB = x2 + B.width; topB = Y1; bottomB = Y1+ B.heigth ; if( bottomA <= topB ) return false; if( topA >= bottomB ) return false; if( rightA <= leftB ) return false; if( leftA >= rightB ) return false; return true; } float move_unit = 0.1; void keyboardown(int key, int x, int y) { switch (key){ case GLUT_KEY_UP: movY2 += move_unit; break; case GLUT_KEY_RIGHT: movX2 += move_unit; break; case GLUT_KEY_LEFT: movX2 -= move_unit; break; case GLUT_KEY_DOWN: movY2 -= move_unit; break; default: break; } glutPostRedisplay(); } void display(){ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); cuad1(); if (!collision) { cuad2(); } else{ reset(); } glFlush(); } int main(int argc, char** argv){ glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(500,500); glutInitWindowPosition(0, 0); glutCreateWindow("Collision Practice"); glutSpecialFunc(keyboardown); glutDisplayFunc(display); init(); glutMainLoop(); }

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  • Refactoring this code that produces a reverse-lookup hash from another hash

    - by Frank Joseph Mattia
    This code is based on the idea of a Form Object http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ (see #3 if unfamiliar with the concept). My actual code in question may be found here: https://gist.github.com/frankjmattia/82a9945f30bde29eba88 The code takes a hash of objects/attributes and creates a reverse lookup hash to keep track of their delegations to do this. delegate :first_name, :email, to: :user, prefix: true But I am manually creating the delegations from a hash like this: DELEGATIONS = { user: [ :first_name, :email ] } At runtime when I want to look up the translated attribute names for the objects, all I have to go on are the delegated/prefixed (have to use a prefix to avoid naming collisions) attribute names like :user_first_name which aren't in sync with the rails i18n way of doing it: en: activerecord: attributes: user: email: 'Email Address' The code I have take the above delegations hash and turns it into a lookup table so when I override human_attribute_name I can get back the original attribute name and its class. Then I send #human_attribute_name to the original class with the original attribute name as its argument. The code I've come up with works but it is ugly to say the least. I've never really used #inject so this was a crash course for me and am quite unsure if this code effective way of solving my problem. Could someone recommend a simpler solution that does not require a reverse lookup table or does that seem like the right way to go? Thanks, - FJM

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  • Are has collisions with different file sizes just as likely as same file size?

    - by rwmnau
    I'm hashing a large number of files, and to avoid hash collisions, I'm also storing a file's original size - that way, even if there's a hash collision, it's extrememly unlikely that the file sizes will also be identical. Is this sound (a hash collision is equally likely to be of any size), or do I need another piece of information (if a collision is more likely to also be the same length as the original). Or, more generally: Is every file just as likely to produce a particular hash, regardless of original file size?

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  • How can I resolve collisions at different speeds, depending on the direction?

    - by Raven Dreamer
    I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c // solve for y. M = 2, x = input's x coord, c = rightYIntercept lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { //change the input vector's x position to match the //y position on the shape's edge. Formula for line: Y = MX+C // M is 2, C is rightYIntercept, y is the input y, solve for X. vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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  • Collision filtering by object, team

    - by Bill Zimmerman
    Hi, I am looking for a good method to determine which objects will be considered for collision with other objects. My current idea is that each object has the following properties: alwaysCollidesWith = [list of objects that will always trigger a collision check] neverCollidesWith = [lost of objects that will never be considered] teamCollidesWith = [list of objects that will be checked, provided they belong to a different team] For example: -projectiles never have to be checked for collisions with other projectiles -players are always checked for collisions with players, regardless of team -projectiles are only considered for collisions if they collide with another teams players Does anyone see any weaknesses with this approach? Can anyone recommend a better approach?

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  • how to create 2D collision detection

    - by Aidan Mueller
    I would like to know the best or most effective way to test for 2D collision. I also can do AABBs but when you have a line, for example, that is rotated 45º, and it is really long. it will be hitting things when it shouldn't. I might be able to go through the pixels to see if they are touching others, but that might be slow if I had a big picture. and it might add some complications if I had a movie clip made of several images. How do I check collision between two Images? How would I do circle to box? Please help : ) PS: I do know java so you can write with java syntax and then use a made up GL

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  • Pong Collision Help in C# w/ XNA

    - by Ramses Brown
    Edit: My goal is to have it function like this: Ball hits 1st Quarter = rebounds higher (aka Y++) Ball hits 2nd Quarter = rebounds higher (using random value) Ball hits 3rd Quarter = rebounds lower (using random value) Ball hits 4th Quarter = rebounds lower (aka Y--) I'm currently using Rectangle Collision for my collision detection, and it's worked. Now I wish to expand it. Instead of it simply detecting whether or not the paddle/ball intersect, I want to make it so that it can determine what section of the paddle gets hit. I wanted it in 4 parts, with each having a different reaction to impact. My first thought is to base it on the Ball's Y position compared to the Paddle's Y position. But since I want it in 4 parts, I don't know how to do that. So it's essentially be if (ball.Y > Paddle.Y) { PaddleSection1 == true; } Except modified so that instead of being top half/bottom half, it's 1st Quarter, etc.

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  • Setting up collision using a tilemap and cocos2d

    - by James
    I'm building my first platformer using cocos2d and a tilemap. I'm having trouble coming up with a decent way of determining if the character is colliding with an object. More specifically, in which direction is the character colliding with an object. Following the tutorial here, I have made a separate "meta" layer of collidable tiles. The problem is that unless the character is in the tile, you can't detect the collision. Also, there's no way of telling WHERE the collision is occurring. The best solution would be one that could tell me if a character is up against a wall, or walking on top of a platform. However, I can't seem to figure out a good technique for this.

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  • Android Touch Event Collision Detection

    - by chrissb
    I'm relatively new to both Java and Android, so hopefully the problem I'm having is stemming from something pretty minor that I've overlooked. I've got a (very early stage) game that I've started working on, for Android using Java. At this stage, when the user touches the screen, if they touched a point at which there is an enemy, the enemies health is decreased and they become immobile (for the current implementation at least). The issue that I'm having is that the touch detection doesn't always seem to work. I've got a testing sprite set up that goes to the eventX and eventY coordinates of the touch down event, and it always seems to collide with the enemy object. Yet, the enemy doesn't always register as being hit, and sometimes a hit is registered when the sprite indicates the touch coordinates were outside of the enemies bounding box. I realise that this probably doesn't mean much without any code, so here's what I've got so far. Be gentle, as this is literally my first attempt at something more than basic movement etc. First off, the MainGamePanel class registers the touch event, and informs the levelmanager class (which is what I set up to monitor/handle enemies) public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN){ levelManager.handleActionDown((int)event.getX(), (int)event.getY()); targetX=event.getX(); targetY=event.getY(); } if (event.getAction() == MotionEvent.ACTION_MOVE) { //the gestures } if (event.getAction() == MotionEvent.ACTION_UP) { //touch was released } return true; } From there, in the levelmanager class the touch event is passed on to all of the enemies within a list array: public static void handleActionDown(int eventX,int eventY){ hit=false; for (enemy1 en : enemy1array){ en.handleActionDown(eventX, eventY); } } The rest of the collision code is handled within the enemies handleActionDown function: public void handleActionDown(int eventX, int eventY) { if(eventX>this.x-enemy1bitmap.getWidth() && eventX<this.x+enemy1bitmap.getWidth() && eventY>this.y-enemy1bitmap.getHeight() && eventY<this.x+enemy1bitmap.getHeight()){ takeDamage(1); levelmanager.setHit(); } } I should probably be using getWidth()/2 and getHeight()/2 for it to be more accurate, but I expanded the area to test this - although I've noticed no improvement. At this stage, the games detection over whether or not the enemy is hit is spotty at best. Generally it takes two or three attempts before a collision is successfully registered, even though the sprite that is being used for testing and set to the eventX and eventY coordinates always indicates that the collision should have worked. Hopefully someone can steer me in the right direction here, and if more information is needed, ask away! Cheers, -Chris

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  • Narrow-phase collision detection algorithms

    - by Marian Ivanov
    There are three phases of collision detection. Broadphase: It loops between all objecs that can interact, false positives are allowed, if it would speed up the loop. Narrowphase: Determines whether they collide, and sometimes, how, no false positives Resolution: Resolves the collision. The question I'm asking is about the narrowphase. There are multiple algorithms, differing in complexity and accuracy. Hitbox intersection: This is an a-posteriori algorithm, that has the lowest complexity, but also isn't too accurate, Color intersection: Hitbox intersection for each pixel, a-posteriori, pixel-perfect, not accuratee in regards to time, higher complexity Separating axis theorem: This is used more often, accurate for triangles, however, a-posteriori, as it can't find the edge, when taking last frame in account, it's more stable Linear raycasting: A-priori algorithm, useful for semi-realistic-looking physics, finds the intersection point, even more accurate than SAT, but with more complexity Spline interpolation: A-priori, even more accurate than linear rays, even more coplexity. There are probably many more that I've forgot about. The question is, in when is it better to use SAT, when rays, when splines, and whether there is anything better.

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  • SFX Played Once per Collision or Hit

    - by David Dimalanta
    I have a question about using Box2D (engine for LibGDX used to make realistic physics). I observed on the code that I've made for the physics here below: @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { // TODO Touch Up Event if(is_Next_Fruit_Touched) { BodyEditorLoader Fruit_Loader = new BodyEditorLoader(Gdx.files.internal("Shape_Physics/Fruity Physics.json")); Fruit_BD.type = BodyType.DynamicBody; Fruit_BD.position.set(x, y); FixtureDef Fruit_FD = new FixtureDef(); // --> Allows you to make the object's physics. Fruit_FD.density = 1.0f; Fruit_FD.friction = 0.7f; Fruit_FD.restitution = 0.2f; MassData mass = new MassData(); mass.mass = 5f; Fruit_Body[n] = world.createBody(Fruit_BD); Fruit_Body[n].setActive(true); // --> Let your dragon fall. Fruit_Body[n].setMassData(mass); Fruit_Body[n].setGravityScale(1.0f); System.out.println("Eggs... " + n); Fruit_Loader.attachFixture(Fruit_Body[n], Body, Fruit_FD, Fruit_IMG.getWidth()); Fruit_Origin = Fruit_Loader.getOrigin(Body, Fruit_IMG.getWidth()).cpy(); is_Next_Fruit_Touched = false; up = y; Gdx.app.log("Initial Y-coordinate", "Y at " + up); //Once it's touched, the next fruit will set to drag. if(n < 50) { n++; }else{ System.exit(0); } } return true; } Now, I'm thinking which part o line should I implement for the sound effects. My objectives to make SFX played once for every collision (Or should I say "SFX played once per collision"?) on the following: SFX played once if they hit on the objects of its kind. (e.g. apple vs. apple) SFX played once on a different sound when it hit on the ground. (e.g. apple land on the mud) Take note that I'm using Box2D for the Java programming version thanks to LibGDX via Box2D engine and I edited the physics body using Physics Body Editor before I implement it to code. I tried to check every available methods for body, fixture definition, or body definition to code for the SFX when hit but it seems only for the gravity and weight. Is there possibly available on the document for SFX played when collision happens if possible?

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  • Pixel perfect collision with paths (Android)

    - by keysersoze
    Hi I'm writing a game and I'm trying to do some pixel perfect collisions with paths. The player's character has a bitmask which looks for example like this: Currenly my code that handles player's collision with path looks like this: private boolean isTerrainCollisionDetected() { if(collisionRegion.op(player.getBounds(), terrain.getBottomPathBounds(), Region.Op.INTERSECT) || collisionRegion.op(player.getBounds(), terrain.getTopPathBounds(), Region.Op.INTERSECT)) { collisionRegion.getBounds(collisionRect); for(int i = collisionRect.left; i < collisionRect.right; i++) { for(int j = collisionRect.top; j < collisionRect.bottom; j++) { if(player.getBitmask().getPixel(i - player.getX(), j - player.getY()) != Color.TRANSPARENT) { return true; } } } } return false; } The problem is that collisions aren't pixel perfect. It detects collisions in situations like this: The question is: what can I do to improve my collision detection?

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  • Collision detection with entities/AI

    - by James Williams
    I'm making my first game in Java, a top down 2D RPG. I've handled basic collision detection, rendering and have added an NPC, but I'm stuck on how to handle interaction between the player and the NPC. Currently I'm drawing out my level and then drawing characters, NPCs and animated tiles on top of this. The problem is keeping track of the NPCs so that my Character class can interact with methods in the NPC classes on collision. I'm not sure my method of drawing the level and drawing everything else on top is a good one - can anyone shed any light on this topic?

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  • HTML5 platformer collision detection problem

    - by fnx
    I'm working on a 2D platformer game, and I'm having a lot of trouble with collision detection. I've looked trough some tutorials, questions asked here and Stackoverflow, but I guess I'm just too dumb to understand what's wrong with my code. I've wanted to make simple bounding box style collisions and ability to determine on which side of the box the collision happens, but no matter what I do, I always get some weird glitches, like the player gets stuck on the wall or the jumping is jittery. You can test the game here: Platform engine test. Arrow keys move and z = run, x = jump, c = shoot. Try to jump into the first pit and slide on the wall. Here's the collision detection code: function checkCollisions(a, b) { if ((a.x > b.x + b.width) || (a.x + a.width < b.x) || (a.y > b.y + b.height) || (a.y + a.height < b.y)) { return false; } else { handleCollisions(a, b); return true; } } function handleCollisions(a, b) { var a_top = a.y, a_bottom = a.y + a.height, a_left = a.x, a_right = a.x + a.width, b_top = b.y, b_bottom = b.y + b.height, b_left = b.x, b_right = b.x + b.width; if (a_bottom + a.vy > b_top && distanceBetween(a_bottom, b_top) + a.vy < distanceBetween(a_bottom, b_bottom)) { a.topCollision = true; a.y = b.y - a.height + 2; a.vy = 0; a.canJump = true; } else if (a_top + a.vy < b_bottom && distanceBetween(a_top, b_bottom) + a.vy < distanceBetween(a_top, b_top)) { a.bottomCollision = true; a.y = b.y + b.height; a.vy = 0; } else if (a_right + a.vx > b_left && distanceBetween(a_right, b_left) < distanceBetween(a_right, b_right)) { a.rightCollision = true; a.x = b.x - a.width - 3; //a.vx = 0; } else if (a_left + a.vx < b_right && distanceBetween(a_left, b_right) < distanceBetween(a_left, b_left)) { a.leftCollision = true; a.x = b.x + b.width + 3; //a.vx = 0; } } function distanceBetween(a, b) { return Math.abs(b-a); }

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  • 2D collision resolving

    - by Philippe Paré
    I've just worked out an AABB collision algorithm for my 2D game and I was very satisfied until I found out it only works properly with movements of 1 in X and 1 in Y... here it is: public bool Intersects(Rectanglef rectangle) { return this.Left < rectangle.Right && this.Right > rectangle.Left && this.Top < rectangle.Bottom && this.Bottom > rectangle.Top; } public bool IntersectsAny(params Rectanglef[] rectangles) { for (int i = 0; i < rectangles.Length; i++) { if (this.Left < rectangles[i].Right && this.Right > rectangles[i].Left && this.Top < rectangles[i].Bottom && this.Bottom > rectangles[i].Top) return true; } return false; } and here is how I use it in the update function of my player : public void Update(GameTime gameTime) { Rectanglef nextPosX = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); Rectanglef nextPosY; if (Input.Key(Key.Left)) nextPosX.X--; if (Input.Key(Key.Right)) nextPosX.X++; bool xFree = !nextPosX.IntersectsAny(Boxes.ToArray()); if (xFree) nextPosY = new Rectanglef(nextPosX.X, nextPosX.Y, nextPosX.Width, nextPosX.Height); else nextPosY = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); if (Input.Key(Key.Up)) nextPosY.Y--; if (Input.Key(Key.Down)) nextPosY.Y++; bool yFree = !nextPosY.IntersectsAny(Boxes.ToArray()); if (yFree) AABB = nextPosY; else if (xFree) AABB = nextPosX; } What I'm having trouble with, is a system where I can give float values to my movement and make it so there's a smooth acceleration. Do I have to retrieve the collision rectangle (the rectangle created by the other two colliding)? or should I do some sort of vector and go along this axis until I reach the collision? Thanks a lot!

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  • libgdx - collision detection with tiled map java

    - by user2875021
    currently, I am working on a 2d rpg game which is similar to final fantasy 1-4. I can load up a tiled map and the sprite can walk freely on the map. However, I will like to create a wall for it to stop walking through it. I created three tiled layer Background, Collision, Overhead and one Collision object layer with rectangles only. "How do I handle collisions with the object layer in the tiled map?" "Do I have to create every single rectangle that is in the object layer with Rectangle rectangle = new Rectangle() and rectangle.set(x, y, width, height)in the code?" Thank you very much in advance. Any help is greatly appreciated!

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